Page 21 - PCA Metro NY Region POST April 2018
P. 21

(rack Ramblings - Continued from page 16 Rev Matching
What is ‘rev matching’ and why is it im- portant? Consider a car which would be
at 3500 rpm in 4th gear at 80 mph and at 4500 rpm at in 3rd at that same speed. Now imagine it is approaching a turn in 4th gear; the driver slows to 80 (3500 rpm) and shifts down to 3rd gear. This car will be (must be) at 4500 rpm when the downshift is com- plete. In order for the shift to be smooth the driver must increase the engine’s speed to 4500 while downshifting. If this rev matching is not done the car will jerk, the tires may chirp for a moment and the car may lose balance. You do not want your car to lose its composure as you are hurtling towards a corner, and particularly in the rain that com- posure is lost very easily.
You can perfect your rev matching tech- nique on the street, so get to it! In that mo- ment while you have depressed the clutch pedal, give a small amount of gas to boost the engine revs up. The tricky part is getting the sense of how much gas is needed in order to attain the lovely smooth downshift.
Heel & Toe
The heel & toe technique is important be- cause without it you can’t brake effectively on the track. Here’s why: Unfortunately we humans were not provided with three feet, at least in respect to downshifting a manual on track, because you need three feet when seriously slowing down – 1 foot of course for the brake, 1 for the gas pedal to match the revs while downshifting, and 1 foot for the clutch pedal (for that downshift).
To get around our lack of sufficient feet, many drivers lift their right foot off the brake pedal and use it to give a quick stab on the gas in order to match revs. Then they resume brak- ing. This gives a smooth shift, which is good, but it makes for poor braking since there is a moment when no braking is occurring.
The heel and toe technique in effect ‘gives
us a third foot’ and allows us to keep press- ing the brake pedal while still being able
to use the left foot for the clutch pedal and also use the right foot for the neces- sary throttle blip. The technique is easy to describe but takes some learning to master. (It is hard to practice on the street since
it is about hard braking from high speeds, which you should only be doing on the track.) The right foot is angled so that the heel is on the gas pedal while the toe is on the brake pedal. You start by applying the brakes (with the toe part of the right foot.) When you have slowed enough to perform the downshift - while you continue braking with your right-foot toes -- you de-clutch as usual with the left foot and then give a little rev matching jab on the gas pedal with the heel of the right foot as you shift down and then let off the clutch pedal. If you do it properly you have continued braking at full intensity and matched the engine revs so that you get a smooth downshift.
If that all sounds complicated, you should be thankful that you aren’t driving a car made prior to 1952 which is when the synchronized (“synchromesh”) gearbox, invented by Dr. Porsche himself, was first made available to the public in the Porsche 356. [It had been utilized by the WW2 Ger- man military in the Kubelwagen often seen in WW2 movies, which was a derivative of the Porsche-designed Volkswagen.] In those ancient days if you wanted to downshift without causing a loud possibly damaging crunch to emanate from the gearbox, you had to “double clutch”. Double clutching is much more complicated than heel & toe. Here are the steps: Say you are in 4th gear approaching a 3rd gear turn. (1) Declutch and shift from 4th gear into neutral; (2) Re- engage the clutch by letting off the clutch pedal; (3) apply gas to match the revs as explained above; (4) declutch and shift from neutral into 3rd gear; (5) Re-engage the clutch; (6) step on the gas and motor away. (Continued on page 32)
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